Posted
by
samzenpus
on Friday November 15, 2013 @03:02AM
from the biggest-there-is dept.

KentuckyFC writes "Until now, the largest known structure in the Universe was the Huge-LQG (Large Quasar Group), a cluster of 73 quasars stretching over a distance of 4 billion light years. Now astronomers say they've spotted something even bigger in data from gamma ray bursts, the final explosions of energy released by stars as they die and the universe's most energetic events. Astronomers have measured the distance to 283 of these bursts and mapped their position in the universe. This throws up a surprise. At a distance of ten billion light years, there are more gamma ray bursts than expected if they were evenly distributed throughout the universe. This implies the existence of a structure at this distance that is about ten billion light years across and so dwarfs the Huge-LQG. What's odd about the discovery is that the Cosmological principle--one of the fundamental tenets of cosmology--holds that the distribution of matter in the universe will appear uniform if viewed at a large enough scale. And yet, structures clearly emerge at every scale astronomers can see. The new discovery doesn't disprove the principle but it does provide some interesting food for thought for theorists."

Given that we have a relatively well developed mathematical articulation of 'random', and the likelihood of various outcomes arising from a random distribution, it should presumably be possible to determine that a given observed outcome is more or less probable as the result of a random distribution. That doesn't necessarily supply any causal suspicion of having arisen other than randomly; but it's still measurable.

"Structure" seems like a poor word, given the heavy connotations of purposeful design or systemic interaction; but choosing a statistical cut-off and taking particular interest in outcomes less probable than that, given the assumptions about the underlying distribution, is in principle sound enough(though it may simply mean that an improbable outcome happened, rather than that the assumptions about the underlying distribution were wrong).

It's like watching the payouts of N slot machines over the course of an evening: If you know, or have a hypothesis, about the odds of the game, you can tell how far a given outcome deviates from the expected distribution, though even observing an extraordinarily unlikely one cannot prove that the game was being rigged, though it can suggest it strongly enough to send you looking for clues in that direction.

I'd like to propose a "hypothesis" that the reason we see these anomalous structures where we should be seeing more randomness would also explain some anomalies we currently blame on dark matter; the influence via gravity of either other dimensions, or extra-Universe objects (basically, other Universes not directly tied to our own). It would mean Gravity is also an "extra dimensional" force or particle that isn't normally observable in our Space/Time.

I'm no cosmologist, so I have no comment there; but the difficultly of looking at what is basically a black box (almost 300 objects at 10 billion light years? Voyager might be a few years away...) statistically is somewhat maddening.

Even a trivially simplified case (say I have a coin, that I allege is fair, and you get to flip it as many times as you want before deciding if you believe me) cannot be decided with certainty. Any finite sequence of flips is equally likely as any other (though sequences that are approximately 50/50 should be overwhelmingly more common if the coin is in fact fair, I have no idea how the behavior changes if you choose infinitely many flips), and you can only gain greater or lesser doubt in the fairness of my coin.

For a much more complex phenomenon, like the origin of the universe, deciding whether you are simply looking at an improbable; but perfectly possible, local perturbation, or whether there is some 'tilt' in the system not covered by current accounts... It's a mathematically cogent exercise; but 'mathematically cogent' and 'easy' are very, very, very different things.

I was attempting emphasis through understatement. Even if Voyager had the correct instruments, it might as well be sitting in my living room for all the difference its travel has made on this kind of scale (and, even if it could reach the site, we'll be waiting a longer than life has so far existed for the reports to come back...)

Unless physics are radically different than suspected, and in a deeply convenient way, something like this is observation only, period, full stop.

Gravitational lensing seems to be one of the major evidences in favor of dark matter/mass, but it'd be interesting to see you (or anyone for that matter) argue that it's just an anomaly given that it can be observed in multiple distinct locations.

(Now, I think we both agree that dark energy is still just a hypothesis, but I think you'd have to come up with something better than claiming that it's "just an anomaly" to explain the existing evidence.

The things being observed are evidence of huge collections of small events (atoms, etc.) So their not being in the predicted distribution is very good evidence that something unexpected is happening. As to WHAT unexpected...that's less clear, which is part of what makes this interesting.

Even at normal human scales, random processes are rare. (Chaotic are less so, and it's often difficult to tell them apart. E.g., I suspect dice throws of being mainly chaotic

But it does test our existing hypothesis. It disconfirms that at a scale of 10 billion light years, matter in the universe is uniformly distributed. If you're into Bayesian epistemology, this means confidence in the Cosmological principle has just been adjusted downwards because of the evidence that has been discovered.

It is of course also important in the formulation of new hypotheses, as you rightly point out, but to imply the one is more important than the other is simply untrue.

I never said it didn't form a test, and I would not hesitate to imply that original thinking in pondering the unknown is always intrinsically more important than endlessly testing the ostensibly "known". Of course, YMMV.

1989http://en.wikipedia.org/wiki/CfA2_Great_Wall [wikipedia.org]The Great Wall (also called Coma Wall), sometimes specifically referred to as the CfA2 Great Wall, is one of the largest known superstructures in the Universe, (the largest being the Huge-LQG). It is a filament of galaxies approximately 200 million light-years away and has dimensions which measure over 500 million light-years long, 300 million light-years wide and 16 million light-years thick, and includes the Hercules Supercluster, the Coma Supercluster and the Leo Cluster.[1]It was discovered in 1989 by Margaret Geller and John Huchra based on redshift survey data from the CfA Redshift Survey.

Yeah, I was just meaning that the CfA Great Wall was superceded by the Sloan Great Wall. If this current structure turns out to genuinely be a structure, it supercedes the Sloan Great Wall by some considerable size.

They didn't discover the largest before; they were just wrong in thinking it was the largest, just like they probably are this time. It's just arrogance to claim it is the largest when one hasn't yet examined the *entire* universe.

Thank God we have people on Slashdot to tell us things like this. Where would we have been if generations of cosmologists were entirely ignorant of statistics or gravitational physics? The mind boggles!

Sorry, but the problem isn't that there are lumps - if there weren't our existence would be a bit suspect since we live on the edge of a reasonably large lump (the Virgo supercluster) ourselves. The problem (if you want to call it a problem; it's more an interesting question) concerns the *size* of the lumps. We can predict with reasonable certainty the probability of a bound structure of such and such a size appearing in the universe. That's quite straightforward in principle. And structures this big are pushing the bounds of the standard cosmological model quite hard; basically, they shouldn't really be there. I don't know the actual probability but it's extremely low, and low enough that we would not expect to see it. That there are now three structures that are rather too large (this one, if it comes to be accepted as a genuine structure; the Sloan great wall, if it turns out to actually be a structure; and the CfA great wall) is getting interesting.

Yes, of course. Thing is that we can't apply that logic here. We know that very large structures are extremely unlikely - in a brute force, frequentist approach which is the nearest analogy to flipping a coin a hundred times, we can make a hundred simulations. If in those hundred simulations we do not see a structure that size, we know that the likelihood of it occuring *within the confines of the model tested* - and that is a very important proviso; we can only assign probabilities in this manner with resp

In the big bang theory there is no outside, so it isn't a lump. Indeed, it's exactly the opposite. In a true "big bang" theory the universe is totally smooth and featureless, and evolving. It's built on "homogeneous and isotropic surfaces". The main observational motivation for this is the microwave background, which to one part in 1000 is identical everywhere we look. That 1/1000 discrepency is a pure dipole -- nothing but a Doppler shift. What *causes* that is mildly debatable, but the effect has to mimic the Earth's motion with respect to the microwave background so closely that an alternative is liable to fall to Occam's razor. In any event, no matter what its source, we know how to remove pure dipoles, so we remove it. And we're left with something that is identical everywhere we look to one part in ten thousand!

So the microwave background is "isotropic" around Earth - everywhere we look it is identical, for all practical purposes. Any model of cosmology has to be able to explain that, and as a bonus also explain what those tiny fluctuations are doing on there and where they came from, and predict their statistical nature. (The big bang theory, plus inflation, does this as perfectly as we could ever ask. No-one seriously suggests that inflation is other than, at best, an effective field theory that describes a more fundamental underlying theory. Well, no-one except people who believe they can boil a moduli inflation out of one string theory or another, but those are still somewhat contrived. But the success of inflation tells us something that acted exactly like it had to happen. (The answer is easy: so-called R^2 inflation. The first inflationary model is believed in the West to be due to Alan Guth, of MIT. This isn't, strictly speaking, true, and Guth would never claim it was. Guth - and Tye - presented the first quantum field theoretical model of inflation, which they based on the Higgs. The first actual inflation came a few years earlier, behind the Iron Curtain, and due to Starobinsky who is a big name in cosmology but deserves to be bigger. Starobinsky was examining what happens when you look at the 'low-energy' limits of a wide variety of modified gravities. General relativity can be described by the equation L=R. Here L is the "Lagrangian density" from which the equations of the theory can be derived while R is the "Ricci scalar" which describes the curvature of spacetime; for comparison, the Lagrangian of normal classical mechanics is L=K-V where K is the kinetic energy and V the potential energy. I'm brushing over the difference between a Lagrangian and a Lagrangian density but it's exactly what it sounds like... Anyway, Starobinsky started from the observation that virtually any modification of gravity will end up reducing, at energies beginning to approach sanity, to something of the form L=R + alpha * R^2 +... where the dots include a wide variety of grotesquely ugly terms alongside the expected R^3. The interesting thing here is that when R gets very large, as would happen in the very early universe, the Lagrangian becomes L=alpha R^2. Solve this and you find you have an exponentially growing universe -- inflation. Study it in more detail, and you find it acts exactly like a more normal inflation (with a potential V proportional to phi^2, I think; it may be phi^4, I forget which), including exactly predicting the form of the perturabtions on the CMB. Actually, if you look at the recent Planck results, R^2 inflation is still stubbornly by *far* the best result... if you judge by eye. Its nearest widely-known competitor is only excluded at the one sigma level, which you'd be laughed at if you seriously tried to say that excluded it, but R^2 lies slap in the middle of every contour and will never be budged from there as long as we live, unless there is a significant detection of cosmological gravitational waves.)

Anyway, I digress.

There are two conclusions we can draw from the CMB:
1) The Earth is at the centre of the Universe. I don't know why religious crazies ne

Yes. That and the primordial density fluctuations were nearly scale-invariant. That is, originally, there were structures of all scales. Gravity over time amplified some of these scales (the most significant being at around 240 million light years), but the natural expectation is still structures at all scales. It would take finding a few extremely large structures that are in excess of the number expected to really throw the standard cosmology into question.

If the bursts happened 10 billion years ago were common all over at that time, (as was asked by the ggp a/c) then the observations would be dirstributed much more randomly across the sky than observation indicates. Observation suggests that the large number of gama ray bursts that happened 10 billion years ago, appear to have happened across a region of space that is heavily weighted in one direction. A circle with a radius of 10 billion light years has a circumfrence of 2*pi*10 billion light years, or a bi

I first heard about the idea of Fractal
cosmology [wikipedia.org] in Mandelbrot's book from 1982, The Fractal
Geometry of Nature. The idea is quite simple: there is
structure at every scale in the Universe, at least up to some
cutoff.

It is kind of funny that some people are surprised when structure
is discovered at larger and larger scales as we are able to make
observations at longer and longer distance scales. It is much
more sensible to expect to see more structure as we see more of
the Universe instead of the m

My laymans understanding is that are processes feedback into themselves, which is what makes fractals. Watched a fun BBC video on on fractals. Plants even space themselves out in fractals, even when inter-species. The size of plants are fractals, the limbs are fractals.. etc etc. They covered a lot of other things, but the whole plant thing stuck the best. Another one was the it seems your hear-beat is based on fractals and non-fractal like hear-beats seem to be highly correlated with heart issues, but more

Are they really that arrogant? Perhaps they just don't know English too well.

I mean, iinm, they previously claimed they had discovered the largest and now they claim it again. There is only *one* largest - it makes no difference if you know about it or not. If you find something new that is larger than what you thought was the largest, then all you have proved is that you were previously wrong. To then claim that the new thing is the largest is arrogant.

What's odd about the discovery is that the Cosmological principle--one of the fundamental tenets of cosmology--holds that the distribution of matter in the universe will appear uniform if viewed at a large enough scale. And yet, structures clearly emerge at every scale astronomers can see.

Beings as we can only ever see a very small fraction of the universe, and don't even know how big it is in its entirety, it's certainly possible we simply can't view a large enough area for the distribution to "even out."

Beings as we can only ever see a very small fraction of the universe, and don't even know how big it is in its entirety, it's certainly possible we simply can't view a large enough area for the distribution to "even out."

If the universe is smaller or larger than the observable universe is still a matter of debate. Quite likely, it will be observations like this that will lead us to the answer by what we can figure out about the very early universe and its expansion.

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
- Douglas Adams, The Hitchhiker's Guide to the Galaxy.

What I never inderstand about articles that talk about very distant objects: they always use "are" as if this large structure would be there now, when, if at all and we interpret the data correctly, it was there billions of years ago. Something that "stretches" over 4 billion ligth years may also (depending on in which direction it stretches) also stretch over a time span of at least 4 billion years.It is weird to think that what we see is not our universe at all: it is a picture that is a collage of times

Since we sit in the light cone for the event currently, to us it does exist now, as it's state 10 billion years ago/10 billion light years away can causely affect us, but not its state 999,999,999 years ago and 10 billion + light years away.

I have issues with the whole report. If the Universe is 13.xG years old, and it's been expanding... 1. How is 31 bursters over 10G ly a "structure"?
2. How big was the Universe 10G years ago? If it was then 10G ly wide, then the expansion is
clearly slowing down, only growing another 3G ly in 10G yrs, after doing 10G ly in 3.xG yrs.

Someone else pointed out that if this one "normal", we would be seeing the same rate of GRB from any direction, but we are not, so it must be true only in that direction, meaning it is something different that normal.

We see power-law scaling everywhere and it looks a lot like the statement in the article. If the size of cars obeyed a power law distribution it would be hard to tell how far you were away from the ground by looking at the apparent size of the cars. The wider you make your gaze the larger cars you will find. We see power-law scaling in continuous phase transition when the system can't really "decide" what scale to prefer so it kind of exists in all scales. Perhaps this means the universe is undergoing s

Must I remind yet again?
The largest structure in the universe is the universe, because it's a subset of itself.
No more largest structure pronouncements, please.
The matter is settled.
Also sprach Zarathustra.

The universe isn't a structure. By "structure" they mean "gravitationally-bound object". The universe is a conglomeration of objects that are not gravitationally-bound. Phrased another way, a "structure" is governed by a metric which is distinctly non-trivial but which you'd hope would be approximated by a Schwarzschild, whereas the universe as a whole is governed by a Robertson-Walker metric which is as trivial as one can get. Put it another way, a "structure" is virialised, while the universe very much i

When they see large structures billions of light years away, then they're also looking back billions of years in time and the universe was a lot smaller then, so they're not really looking at something that large, they're looking at something that was small and has been stretched out subsequently, so these reports of 'large structures' don't make sense.

But don't worry, most people stupid enough not to understand that it's still better to try follow the scientific method than to just invent concepts and believe them, don't read Slashdot. so it won't be us who'll have to deal with them.

Science is the systematic observation of everything in our world and universe; it is the best and most successful way we have discovered for determining what is true and what is not. That does not mean that it cannot make mistakes, but it does mean that mistakes can be noticed, making it a self-correcting process, trudging ever forward towards greater accuracy and understanding. Pointing out that science makes mistakes is pointing out a part of how the scientific process works and achieves progress; it's not a bane, it's a boon.

Yep, if only that were widely understood... I'd like to see more things prefaced with, "Here's what we think we know as of today..." in order to help the larger population realize it's good to question things and continue researching, developing, and exploring. Often the first whack or two are not particularly correct.

That's true, which is why I'm not making it. I don't adhere to Popper's views on the philosophy of science in the main, but I think the idea of verisimilitude (we're only ever approaching reality closer and closer, but may never get 100% accurate descriptions) is spot on. Science is for claims about accuracy, and predictive and explanatory power. The Truth is in the domain of metaphysics.

And then I expanded upon my conception of truth as I used it there later with the part about achieving greater accuracy. However, since I realize that this is not necessarily the standard idea of The Truth as others might conceive of it, I then made my views explicit in the follow-up by distinguishing those two conceptions of truth.

Meanwhile Dawkins is so confident of the *truth* of his extrapolatory creation myth that he feels the need to call believers of any other extrapolatory creation myth "deluded"... while the details of his myth get rewritten every 5-10 years.

Yes. And it's justified.(a) just because two things are extrapolatory doesn't mean they are supported by equivalent qualities of models nor quantities of data.(b) the Bible is not extrapolatory. it just states.(c) the details of Big Bang and Evolution may get rewritten c

I just think it's ironic that people have to state "what science is" on Slashdot. I'm not criticizing the practice -- I'm concerned by how much we NEED to inform people of WHY science is good, even if it is never settled, and what the scientific process is.

This is just sad. This is a culture in decline. Forget about Rock Music, long hair, tattoos -- whatever shocking thing the next generation comes up with; SCIENCE is one of the first targets of a society in decline.

We never had that.At best, we had precious few enlightened men during some ages. Everyone else always danced and still dances to the witchdoctor's drum.

Presently we are in an age where we have more enlightened men than ever before - but we also have a lot more witchdoctors and dancers.But we did win a battle or two along the way.E.g. You won't be burned at a stake for using a match or a lighter any more, or be accused of stealing someone's soul when taking a photo of them.It adds up.